System for the contactless sealing of a rotatably mounted shaft with respect to a housing, and gear unit

ABSTRACT

A system for the contactless sealing of a rotatably mounted shaft with respect to a housing, and a gear unit, oil being provided in the interior of the housing, in particular, the rotating shaft protruding from the interior into the outer area; a centrifugal disk, joined in rotatably fixed manner to the shaft, having at least partially radially extending bores that connect oil from a centrifugal chamber to a collection chamber surrounding the centrifugal disk.

FIELD OF THE INVENTION

The present invention relates to a system for the contactless sealing ofa rotatably mounted shaft with respect to a housing, and a gear unit.

BACKGROUND INFORMATION

In sealing systems having shaft sealing rings, it is well-known thatfriction losses increase as the rotational speed increases.

German Published Patent Application No. 602 16 474 describes acontactless sealing in which a centrifugal disk, having radial bores asslinger ports (FIG. 1 there, reference 44), is provided on a shaft. Theradial bores permit lubricating oil, which was accumulated in a radiallyinner centrifuging chamber, to flow out, the bores then centrifuging theoil off at their other end area into a collection chamber. Thecentrifugal disk has an axial gap with respect to a non-rotating part,the gap joining the centrifuging chamber to the collection chamber.

A labyrinth seal is described in German Published Patent Application No.479 388.

U.S. Pat. No. 2,598,381 describes connecting an interior space of a gearunit, partially filled with lubricating oil, via an air channel (FIG. 1there, reference numeral 9) to the outside air, for example, forcompressed-air compensation. In that case, oil is conveyed radially andaxially inward by centrifugal force, by providing a suitable bevel.Independently of this air channel, a contactless sealing is achieved bya centrifugal edge which, during rotational movement, centrifuges theoil off into a collection chamber (FIG. 1 there, reference numeral 13)that is connected by a downward running bore to the oil-pan space.

German Published Patent Application No. 10 2007 014 657 describes ashaft sealing device in which oil, likewise centrifuged off, isrecirculated.

German Published Patent Application No. 698 18 914 describes a shaftsealing system in which a shaft sealing ring is provided.

A sealing ring for a water-pump bearing is described in German PublishedPatent Application No. 601 30 871.

German Published Patent Application No. 42 20 754 also describes asealing system that functions in non-contact fashion during rotationalmovement of the shaft of a gear unit, in which oil, likewise centrifugedoff, is recirculated.

German Published Patent Application No. 39 30 280 likewise describessuch a sealing system functioning in non-contact fashion duringrotational movement of the shaft.

A sealing system acting in contacting fashion is described in GermanPublished Patent Application No. 35 44 783.

A sealing system that functions in non-contact fashion during rotationalmovement of the shaft, in which oil, likewise centrifuged off, isrecycled is also described in German Published Patent Application No. 3330 473.

German Published Patent Application No. 11 2004 000 627 also describes asealing system that functions in non-contact fashion during rotationalmovement of the shaft, and in which oil spun off by a plurality of shaftgrooves is likewise recycled.

A sealing system that functions in non-contact fashion during rotationalmovement of the shaft and in which oil spun off by pointed edges islikewise recirculated is described in German Published PatentApplication No. 470 121, as well.

U.S. Pat. No. 5,538,258 describes a contactless sealing in which acentrifugal disk, having radial bores as slinger ports (FIG. 1 there,reference numeral 44), is provided on a shaft. The radial bores permitlubricating oil, which was accumulated in a radially inner centrifugalchamber, to flow out, the bores then ejecting the oil at their other endarea into a collection chamber. The centrifugal disk has an axial gapwith respect to a non-rotating part, the gap joining the centrifugalchamber to the collection chamber.

SUMMARY

Example embodiments of the present invention reduce maintenance costsand losses in the case of a sealing system.

Among features of example embodiments of the present invention withregard to the system are that it is provided for the contactless sealingof a rotatably mounted shaft with respect to a housing, oil beingprovided in the interior of the housing,

in particular, the rotating shaft protruding from the interior into theouter area,

wherein

a centrifugal disk, joined in rotatably fixed manner to the shaft, hasat least partially radially extending bores that connect oil from acentrifugal chamber to a collection chamber surrounding the centrifugaldisk.

In particular, a centrifugal disk, joined in rotatably fixed manner tothe shaft, thus has bores extending at least partially in the radialdirection, so that lubricating oil is able to be conveyed from acentrifugal chamber to a collection chamber surrounding the centrifugaldisk,

the bores opening through with their radially inner end area into thecentrifugal chamber, and opening through with their radially outer endarea into the collection chamber,

between the centrifugal disk and a flange part of the housing, a gapregion being provided which

-   -   connects the centrifugal chamber to the collection chamber and    -   into which a bore leads with its first end area, the bore        opening through with its other end area into a further        collection-chamber area, so that lubricating oil, centrifuged        off into the further collection-chamber area by a centrifugal        edge joined in rotatably fixed fashion to the shaft, is able to        be collected and fed through the bore to the gap region,

a gap region connecting the further collection-chamber area to thecentrifugal chamber.

The bore between the gap region and the further collection-chamber areapreferably extends axially.

Of advantage is that the oil is able to be conveyed out of a centrifugalchamber—which at least partially surrounds the centrifugal disk and isbounded by housing parts and the shaft or centrifugal sleeve provided onthe shaft—through the centrifugal disk, namely, through bores in thecentrifugal disk. Thus, effective emptying of the centrifugal chamber isattainable. In so doing, the oil is emptied out not into the oil-panarea or the interior space, e.g., into the interior of the gear unit,but rather into a collection chamber, therefore, a spatial area which isbounded by the flange parts and the rotating part, thus, the shaft or acentrifugal sleeve provided on the shaft.

In this manner, it is possible to avoid wear to the seal, particularlyin comparison to shaft sealing rings which are subject to wear.Furthermore, maintenance costs are improved and reliability is likewiseimproved.

It is further advantageous that oil, which is caught in a collectionchamber situated axially further outside, is able to be fed into the gapregion between the co-rotatable centrifugal disk and the stationaryflange part. Since this gap region extends radially, a pressure gradientexists between the centrifugal chamber and the collection chamber thathas a conveying effect which acts as return. Thus, even if oil on thecentrifugal disk were to arrive further axially to the outside, a returnfrom a downstream collection chamber would be made possible through thebore between the gap region and the collection-chamber area.

An advantage is that an active pumping action is attainable, accompaniedby a contactless sealing.

In example embodiments, the centrifugal disk is secured on a centrifugalsleeve which is provided on the shaft. This is advantageous becauseassembly is easy, and in addition, diameter variations, such as an axialarea with increasing or decreasing diameter, may be produced in aninexpensive and uncomplicated manner. The reason is the centrifugalsleeve does not pass any substantial torque through, the centrifugaldisk being secured on the centrifugal sleeve, however. Thus, centrifugalgrooves are able to be provided easily and inexpensively in thecentrifugal sleeve, as well.

In example embodiments, the centrifugal chamber is bounded at leastpartially by a channel running round on the centrifugal disk, thechannel being formed as the local maximum of the radial distance of thesurface of the centrifugal disk; thus, in particular, the radialdistance of adjacent surface areas of the centrifugal disk increaseswith decreasing axial distance toward the channel. This offers theadvantage that oil propelled by the centrifugal force is driven intothis channel, and from there, is then conveyed away with the aid of thebores.

In example embodiments, at least in one axial partial area, the outsidediameter of the centrifugal sleeve increases toward the centrifugaldisk, particularly with the aid of a chamfer provided on the centrifugalsleeve, especially so that oil is conveyed in the direction of thecentrifugal disk, especially in the direction of the channel of thecentrifugal disk. The advantage in this context is that a conveyingaction is able to take place in the direction of the channel, andtherefore the oil is able to be discharged, especially in an easymanner, via the associated bore in the centrifugal disk, into thecollection chamber.

In example embodiments, provided between the centrifugal disk and aflange part of the housing is a gap region, especially a radiallyextended gap region, into which a bore leads that is connected to acollection groove, thus a collection-chamber area, provided in theflange part,

in particular, the bore being situated at smaller radial distance thanthe radial distance of the end area of the gap region, which opensthrough into the collection chamber, in particular, the collectiongroove being provided axially further outside than the centrifugal disk.The advantage in this case is that a pumping action is attainable in thegap region, since the gap region is bounded at a first lateral surfaceby the centrifugal disk, and at the lateral surface opposite this firstlateral surface, by the housing part that does not co-rotate, thus,especially the outer flange part. Therefore, an underpressure isobtained for emptying the bore leading in, in the direction of thecollection chamber connected at greater radial distance.

In example embodiments, a gap is provided between the centrifugal sleeveand a further flange part joined to the flange part, the gap beingimplemented as a radial gap in a first partial area, and as an axial gapin a further partial area. This is advantageous in that oil musttraverse the radial gap coming from outside to the inside, since the endarea of the radial gap with greater radial distance is disposed towardthe interior, and the end area of the radial gap with smaller radialdistance must first be reached against the centrifugal force.

In example embodiments, the gap opens through into a collection groovethat is provided in the further flange part and is connected to thecollection chamber via a further gap which is situated between thefurther flange part and the centrifugal sleeve. The advantage here isthat the gap represents a further barrier for penetrating oil. Inparticular, it may be implemented as a capillary gap, and therefore alsorepresents a barrier very difficult to overcome.

In example embodiments, the collection chamber is connected in its lowerarea via a bore to the interior of the housing, especially to theoil-pan area. This is advantageous because oil which has penetrated orbeen caught in the collection chamber is able to be evacuated to the oilpan, especially driven by the force of gravity.

In example embodiments, the flange parts are screw-connected and a seal,especially an O-ring seal, is disposed between them. The advantage hereis that the housing may be made strong and leak-proof. In particular,the joint of the two flange parts is sealed up, so that the O-ring seallies further inside in the joining surface and the screw connection liesfurther outside. Therefore, no oil penetrates from the interior spacevia the joining surface, thus the contact surface, to the thread area ofthe screw, and from there into the outer area. FIG. 1 shows a screwpassing through from the outer area through the outer and the innerflange part. In a further improved exemplary embodiment, the screw doesindeed penetrate through the outer flange part, but is screwed into anon-through bore in the inner flange part.

In example embodiments, a first baffle area having a first drainagechannel is disposed on the further flange part, in particular, a secondbaffle area having a second drainage channel being disposed on thefurther flange part, the baffle area and drainage channel in particularbeing axially symmetric. This offers the advantage that each baffle areais able to be provided combined with a corresponding drainage channel,so that the liquid portions which have struck are able to be carriedaway quickly and easily. Therefore, the main quantity of the oil sprayedaround during operation above the oil level is able to be collected andrecirculated, particularly at the periphery of the overall sealingsystem.

In example embodiments, in each case a centrifugal groove is disposed onthe centrifugal sleeve, radially opposite the collection groove(s). Thisis advantageous, because the centrifugal groove may be produced easilyand inexpensively.

In example embodiments, the gap regions are each implemented ascapillary gap regions. The advantage here is that the resistance to flowfor oil is very high, and this is therefore hindered in respect to theat least rapid flow through the gap.

In example embodiments, a dust protector, which is in contact with theflange part, is disposed on the shaft. The advantage in this case isthat the functioning method of the sealing system is not disturbed, forin the event great quantities of dust penetrate, a bore could be stoppedup, for example. The spatial area protected by the dust protector isconnectable directly or with the aid of a gap to a collection groove orto some other collection area such as the collection chamber, forinstance.

The dust protector does not contribute to the actual sealing action ofthe sealing system, for it protects only against penetrating dust andcontacts the flange part, belonging to the housing, at its outersurface.

In example embodiments, the oil level lies below—thus below in thegravitational direction—the system when the gear unit is at rest. Theadvantage in this context is that in the state of rest, there is nopossibility that oil will pass through the sealing system, and thenpenetrate into the outer area.

LIST OF REFERENCE NUMERALS

-   1 Shaft-   2 Axial gap, capillary gap region-   3 Entry labyrinth, including radially extended gap section,    capillary gap region-   4 Drainage channel-   5 Calming space-   6 Baffle surface-   7 Collection groove-   8 Drainage channel-   9 Baffle surface-   10 Collection chamber-   11 Centrifugal bore-   12 Gap, particularly radial gap, capillary gap region-   13 Collection groove, further collection-chamber area-   14 Third centrifugal groove-   15 Second centrifugal groove-   16 First centrifugal groove-   17 Dust protector-   18 Inner return bore-   19 Flange, outer sealing flange-   20 Retaining screw-   21 Outer return bore-   22 Centrifugal disk-   23 Inner sealing flange, further flange part-   24 Drain bore-   25 Centrifugal sleeve-   26 O-ring seal-   27 Centrifugal chamber-   28 Chamfer-   29 Widening

Example embodiments of the present invention are explained in greaterdetail with reference to the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system according to an example embodiment of thepresent invention.

FIG. 2 is an enlarged cross-sectional view of the system illustrated inFIG. 1.

DETAILED DESCRIPTION

A system according to an example embodiment of the present invention isshown schematically in FIG. 1. An enlarged section is shown in FIG. 2.

According to example embodiments of the present invention, a contactlesssealing is attained between a rotating shaft 1 and a housing.

In this context, disposed on shaft 1 is a centrifugal sleeve 25 onwhich, in addition, a centrifugal disk 22 is situated, in particular,joined with material locking or as a press-fitted connection.

An outer sealing flange 19 and an inner sealing flange 23 are providedon the housing, the centrifugal disk being set apart from outer sealingflange 19 by a gap 12, and centrifugal sleeve 25 being set apart frominner sealing flange 23 by a gap, including entry labyrinth 3 and axialgap 2.

The sealing system is set up in multiple stages, and in this manner, theoil passing through each obstacle is in each instance met with a furtherobstacle.

The entire sealing system is disposed above the oil level which sets inwhen shaft 1 is at rest. During operation of shaft 1, oil foam orspraying oil may be produced, for example, by gear wheels connecteddirectly or indirectly with the shaft. Preferably, this oil level isbelow return bore 21.

The oil striking against baffle surface 9 is drained off via anannularly formed drainage channel 8, and downward toward the oil pan.

Provided axially somewhat further inside, but radially deeper, is bafflesurface 6, which is bounded radially to the inside by an annular calmingspace 5 that has a drainage channel 4 situated radially inside. Entrylabyrinth 3, which is provided between centrifugal sleeve 25 and innersealing flange 23, begins directed inwards in the axial direction, thengoes over into a radially running section and ends as axial gap 2situated radially further inside, which then runs directed outwards inthe axial direction, and at its end area, widens in the direction ofcollection groove 7. The flaring, thus the widening denoted by referencenumeral 29, is realized by a suitable chamfer, so that the capillaryeffect is interrupted in this area. A centrifugal groove 16 is disposedon centrifugal sleeve 25, opposite collection groove 7, and is providedto spin oil off in the direction of collection groove 7. At the lowerarea of collection groove 7, a drain bore is provided that is aligned inthe axial direction and leads into a collection chamber 10, which inturn returns oil via a bore, namely, outer return bore 21 in innersealing flange 23, back into the oil pan.

Between centrifugal sleeve 25 and inner sealing flange 23, a gap isprovided that connects collection groove 7 to collection chamber 10.

A centrifugal groove 15 is again disposed in the axial region ofcollection chamber 10, so that oil which penetrates via the indicatedgap is centrifuged off.

In addition, provided axially following is centrifugal disk 22 thatlikewise centrifuges oil off into collection chamber 10.

Axially following centrifugal disk 22, a further centrifugal groove 14is again provided, opposite which a collection groove 13 is located onflange part 19. Thus, oil is spun off from the edges of centrifugalgroove 14 into collection groove 13.

Centrifugal sleeve 25 is implemented with a chamfer 28 such that itsoutside diameter increases in an axial area which is located betweencentrifugal groove 14 and centrifugal disk 22, and specifically,increases with decreasing distance to centrifugal disk 22, so that oilpossibly appearing is conveyed in this direction, thus, towardcentrifugal disk 22. Therefore, chamfer 28 contributes in connectionwith the return flow. The oil is then conveyed into centrifugal chamber27, which is emptied into collection chamber 10 with the aid ofcentrifugal bores 11 that are introduced into centrifugal disk 22 in theradial direction. A plurality of such centrifugal bores 11, especiallybetween four and twenty, are provided at the periphery of thecentrifugal disk.

Collection groove 13, situated axially further to the outside, has atits lower region, especially including the deepest point, a bore 18directed axially toward the gap region, thus, gap 12, which is providedbetween centrifugal disk 22 and outer flange 19. Collection groove 13 isassigned a centrifugal groove 14, which is provided on centrifugalsleeve 25.

This gap region of gap 12 is open toward collection chamber 10. Sincebore 18 discharges into gap region 12 at a radial distance that issmaller than the radial distance of radially outside end area of gapregion 12, where gap region 12 discharges into collection chamber 10, aconveying effect is provided. The reason is that due to the rotationalmovement, an underpressure is generated, which causes bore 18, andtherefore collection groove 13, to be pumped out.

Thus, not only is the well-known centrifuging provided for thedischarge, but also the pumping effect of a gap region 12.

Collection grooves 7 and 13 are therefore emptied into collectionchamber 10, and not directly into the interior and/or the oil-pan area.To that end, bore 24 connects collection groove 7 to collection chamber10.

Inner sealing flange 23 and outer sealing flange 19 are joined to eachother, sealed off by an O-ring seal 26, a plurality of successiveretaining screws 20 in the circumferential direction joining the twosealing flanges. Thus, a one-piece construction of the two sealingflanges 19 and 23 is also possible. A dust protector 17 is just providedexternally.

A further collection-chamber area is formed by collection groove 13,that is situated separate from collection chamber 10 and is providedfurther axially outwards.

What is claimed is:
 1. A system for contactless sealing of a rotatablymounted shaft with respect to a housing, an interior of the housingbeing filled at least partially with lubricating oil, comprising: acentrifugal disk, joined in rotatably fixed manner to the shaft, havingcentrifugal bores extending at least partially in a radial direction, sothat the lubricating oil is conveyable from a centrifugal chamber to acollection chamber at least partially surrounding the centrifugal disk,the centrifugal bores opening through with a radially inner end areainto the centrifugal chamber, and opening through with a radially outerend area into the collection chamber, a gap region arranged between thecentrifugal disk and a flange part of the housing, the gap regionconnecting the centrifugal chamber to the collection chamber, a bore onthe housing and leading into the gap region, that with its other endarea opens through into a further collection-chamber area, so thatlubricating oil centrifuged off into the further collection-chamber areaby a centrifugal edge joined in rotatably fixed fashion to the shaft iscollectable and feedable through the bore to the gap region; and a gapregion connecting the further collection-chamber area to the centrifugalchamber.
 2. The system according to claim 1, wherein the centrifugaldisk is secured on a centrifugal sleeve that is provided on the shaftand includes centrifugal grooves.
 3. The system according to claim 2,wherein at least in one axial partial area, an outside diameter of thecentrifugal sleeve increases toward the centrifugal disk with the aid ofa chamfer provided on the centrifugal sleeve, so that oil is conveyablein at least one of (a) a direction of the centrifugal disk and (b) adirection of a channel of the centrifugal disk.
 4. The system accordingto claim 1, wherein the gap region is arranged as at least one of (a) aradial gap and (b) a radially extended gap region, the furthercollection-chamber area being formed by a collection groove provided inthe flange part, the bore being situated at a smaller radial distance toa shaft axis than a radial distance of an end area of the gap regionwhich opens through into the further collection-chamber area, thecollection groove being provided axially further outside than thecentrifugal disk.
 5. The system according to claim 1, wherein a gap isprovided between the centrifugal sleeve and a further flange part joinedto the flange part, the gap extending radially in a first partial areaand axially in a further partial area.
 6. The system according to claim5, wherein the gap opens through into a collection groove which isprovided in the further flange part and is connected to the collectionchamber via a further gap disposed between the further flange part andthe centrifugal sleeve.
 7. The system according to claim 1, wherein thecollection chamber is connected in a lower area via a bore to at leastone of (a) the interior of the housing and (b) an oil-pan area.
 8. Thesystem according to claim 5, wherein the flange part and the furtherflange part are screw-connected, and a seal is disposed between theflange part and the further flange part.
 9. The system according toclaim 5, wherein a first baffle area, having first drainage channel, issituated on the further flange part, a second baffle area having seconddrainage channel being disposed on the further flange part, the baffleareas and the drainage channels being axially symmetric.
 10. The systemaccording to claim 1, wherein each collection groove is assigned aparticular intended centrifugal groove located radially opposite on thecentrifugal sleeve.
 11. The system according to claim 1, wherein the gapregions are arranged as capillary gap regions.
 12. The system accordingto claim 1, further comprising a dust protector in contact with theflange part disposed on the shaft.
 13. The system according to claim 1,wherein at one axial end area of a gap region that is arranged as acapillary gap, a widening is provided which is arranged such that acapillary effect is interrupted in an area of the widening.
 14. A gearunit, comprising: a system according to claim 1; wherein, when the gearunit is at rest, an oil level lies below in a gravitational directionthe system.